Apparatus and method for determining the soil resistance of a subterranean earth formation

ABSTRACT

APPARATUS AND METHOD FOR DETERMINING THE SOIL RESISTANCE OF A SUBTERRANEAN EARTH LAYER BY DRIVING A SOUNDING PIN CARRIED BY A BODY INTO THE LAYER UTILIZING THE WEIGHT OF THE BODY TO DRIVE THE PIN THROUGH THE LAYER. THE FORCES EXERTED ON THE PIN ARE MEASURED AND RECORDED AND SOIL WITHIN THE LAYER IS WASHED AWAY WHILE DRIVING THE PIN THERETHROUGH.

Oct- 12, 1971 P. J. DE GEL-:TER

APPARATUS AND METHOD FOR DETERMINING THE SOIL RESISTANCE OF ASUBTERRANEAN EARTH FORMATION 3 Sheets-Sheet 1 Filed Sept. 23, 1969 FIG.2

L w 5 O 5 4 5 3 5 4 m. 6 5 .\4 7 8 5 4 uw 6 5 I f M M 4 9 3 4 5 7 3 4 2n 9 2 I /q//r f IIL l IIITIIII l IJ 7 4 f H 19|. m 9 2 FIGl 3 FIG.

INVENTOR:

P|ETER J. DEGEETER BY:

@ZW )PEM/MM Has ATTORNEY Oct. 12, 1971 p, 1 DE GEETER 3,611,794

APPARATUS AND METHOD FOR DETERMINING THE SOIL RESISTANCE OF ASUBTERRANEAN EARTH FORMATION Filed Sept. 23, 1969 .'5 Sheets-Sheet .'3

72 RTW/4 /f n f/ y es nl 5 e7 i f fr lxs 76/ a l Y M75 f, a 75/ a 4 i'.r/ /8o E /sl 7 74/ r/74 5 f 'l 64 g Y,79

78 iff# INVENTOR:.

PIETER J. DEGEETER JW XW,

HIS ATTORNEY Oct. 12, 1971 p, DE GEETER 3,611,794

APPARATUS AM) METHOD FOR DETERMINING THE SOIL RESISTANCE OF ASUBTERRANEAN EARTH FORMATION 3 Sheets-Sheet Z Filed Sept. 23, 1969 FIG.

FIG. 9

FIG-8 FIG. 7

FIG. II

INVENTOR:

PIETER J. DEGEETER, BY: J

. I5 OQSMJJ HIS ATTORNEY Unted States Patent @mee 3,611,794 PatentedOct. 12, 1971 U.S. Cl. 73-84 6 Claims ABSTRACT or THE DISCLOSUREApparatus and method for determining the soil resistance of asubterranean earth layer by driving a sounding pin carried by a bodyinto the layer utilizing the weight of the body to drive -the pinthrough the layer. The forces exerted on the pin are measured andrecorded and soil within the layer is washed away while driving the pintherethrough.

BACKGROUND OF THE INVENTION iField of the invention The presentinvention relates to a method and apparatus for determining the soilresistance of subsurface layers. Particularly, the present inventionrelates to a method and apparatus for determining the soil resistance ofsubsurface layers by means of a sounding pin carried by a body fordriving the pin through the soil.

Description of the prior art The knowledge of soil resistance or bearingcapacity of the soil is of particular interest when erecting heavystructures. vIt is then of utmost importance to know the resistance orbearing capacity of the soil at the site where the structure is to beerected. If, for instance, it is desired to set up a platform supportedby legs on the bottom of the sea, such as is often required whendrilling oil or gas wells, or when producing oil or gas from such wells,it is iirst necessary to investigate the ability of the sea bottom tosupport the platform legs in such a way that no impermissible subsidenceof those parts of the sea bottom carrying the legs will take place.

It will be appreciated that the requirements for measuring the bearingcapacity of the soil apply for marine work as described above as well asfor land work.

SUMMARY OF THE INVENTION lIt is an object of this invention to provide`a method and apparatus for measuring bearing capacities, by which arecord of the bearing capacity of subsoils may be obtained as a functionof their depth. v

It is a further object of the present invention to provide a method andapparatus measuring the properties of subsurface formations wherein thisinformation may be obtained in a very simple and quick manner.V

According to the invention, the sounding pin is driven through the soilunder influence of at least part of the Weight of the body carrying thepin, and the soil at a level between the lower end of the body and lthelower end of the sounding pin is washed away by hydraulic jets to form ahole for the free passage of the body.

The soil may be washed away by hydraulic iets to a level just below thelower end of the sounding pin when the sounding pin has to be driventhrough relatively hard layers odering a resistance to the sounding pinwhich is higher than the downward load exerted in the body on thesounding pin. n

The body may be suspended from a flexible tubular element rwhich is runat a substantially*constant'velocity into the hole in which the bodydriving the sounding pin descends.

The present application further relates to apparatus for determining thesoil resistance of subsurface layers comprising a sounding pin carryingelements for measuring forces exerted on the pin, recording means forrecording the values of the forces exerted on the pin, a body carryingthe sounding pin at one end thereof, at least one nozzle carried by thebody at the end carrying the sounding pin, a flexible conduit connectedto rthe other end of the body and a passageway forming a communicationbetween the interior of the [flexible conduit and the nozzle.

The apparatus according to the invention may further" comprise a secondnozzle or set of nozzles communicating via a second passageway with theiirst passageway, a valve being arranged in this second passageway whichvalve may be opened by a relative displacement between the sounding pinand the body, and may be closed by a relative displacement between thepin and the body in a sense contrary to the sense of the rstdisplacement.

In, another embodiment, the apparatus according to the inventioncomprises a second nozzle or set of nozzles communicating with theinterior of the ilexible conduit via a second passageway, a valve beingarranged in said second passageway and the flexible conduit, which valvemay be opened by a relative displacement between the sounding pin andthe body, and may be closed by a relative displacement between the pinand the body in a sense contrary to the sense of the rst displacement.

In still another embodiment, the apparatus according to the inventioncomprises a second nozzle or set of nozzles communicating with theinterior of a second exible conduit via a second passageway, a valvebeing arranged in said second passageway, which valve may be opened by arelative displacement between the sounding pin and the body, and may beclosed by a relative displacement between the pin and the body in asense contrary to the sense of the rst displacement.

A second valve may be arranged in the rst passageway which valveco-operates with the first valve so as to close the passage through theiirst passageway when the passage through the second passageway is beingopened by the first Valve and vice versa.

The valve (or valves) may be coupled to the sounding pin and be loadedby a spring. The valve(s) may also be loaded in the normal workingposition lby hydraulic pressure to close the valve arranged in thesecond passageway.

*In another embodiment of the invention, the sounding pin istelescopically arranged with respect to the body between two positions,and loading means are provided urging the pin to the position in whichthe pin protrudes as farl as possible from the body.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a vertical sectional view ofthe body and the sounding pinA carried thereby, of an apparatusaccording to the invention;

FIG. 2 is a vertical side view of a frame carrying guide wheels suitablefor guiding the ilexible conduit carrying the body and the sounding pinof FIG. 1;

AFIG. 3 is a top plan view of the frame of FIG. 2;

FIG. 4 is a vertical sectional view of apparatus according to theinvention wherein the valves arranged in the passageway leading to afirst and a second set of nozzles respectively are biased by hydraulicpressure;

FIG. 5 is a view similar to FIG. 4 but with the valves in a diiferentposition;

FIG. 6 is a View similar to FIG. 4, but with the valves in such aposition that the passageway leading to the rst set of nozzles is closedand the passageway leading to the second set of nozzles is open;

FIG. 7 is a vertical sectional view of a body'and sounding pin vofapparatus according to the invention, which is provided with a singleset of nozzles, and in which the pin is automatically retracted whenrelatively hard layers of the formation are to be passed;

FIG. 8 is a vertical sectional, partly schematic, view of the apparatusaccording to FIG. 7 in a position in which the pin has touched a.relatively hard formation layer;

FIG. 9 is a vertical sectional, partly schematic, view of the apparatusaccording to FIG. 7, in which the pin is in the retracted position;

FIG. 10 is a vertical sectional, partly schematic, view of the apparatusaccording to FIG. 7, when passing through the relatively hard layer;

FIG. 11 is a vertical sectional, partly schematic, view of the apparatusaccording to FIG. 7, in a position wherein the pin has passed throughthe relatively hard layer; and

FIG. 12 is a vertical sectional, partly schematic, view of the apparatusaccording to FIG. 7, wherein the body has passed through the relativelyhard layer.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the apparatus according toFIG. 1, the sounding pin y1 is connected to the lower end of a body 2 bymeans of a telescoping arrangement. This arrangement comprises athickened end 3 of the sounding pin 1, which thickened end at the lowerside thereof is provided with a. valve body 4 and with its upper partmay slide within the cavity 5 formed by a housing 6 which is connectedto the inner side of the wall 7 of the body 2 by distance pieces 8. Thevalve body 4 cooperates with a valve seat 9 which is formed on the lowerpart 10 of the body 2. This lower part 10 is connected to the body 2 ina suitable (not shown) manner so as to partly close off the open side ofthe cavity 11 of the body 2, thereby leaving open a circular row ofnozzles 12 arranged near the wall 7 of the body 2. The nozzles 12 aredirected downwards when the sounding pin 1 is in its operationalposition. The part 10 further forms a nozzle 13 around the sounding pin1, which nozzle has the supply thereto closed-off by the valve body 4when the sounding pin is pressed downwards by the spring 14. This spring114 is compressed between the thickened end 3 of the sounding pin 1 andthe inner end wall 6a of the housing 6 surrounding'the cavity 5. Thevalve body 4 may be opened by depressing the sounding pin .1 relative tothe body 2 thereby further compressing thespring 14.

The nozzles 12 are at one side thereof in communication with the cavity11 which in its turn communicates via a bore 15 in the body 2 with theinterior 16 of a exible conduit 17. The lower end of this conduit isclamped to the body 2 by a suitable clamping means 18.

At least two electric cables 19 and 20 are incorporated in the wall ofthe flexible conduit 17. The cable 19 is grounded to the body 2 by meansof a suitable screw 21, whereas the cable 20 is passed suitablyinsulated into a watertight coupling unit 22, in which unit the conduit20 is connected to an insulated cable 23, which at its other end isconnected to the one end of the electric circuit of a straingauge 24(see dotted lines in FIG. 1) connected to the sounding pin 1. The otherend of the electric circuit of the straingauge 24 is grounded via cable-25 to the sounding pin I1, and since the pin 1, valve 4, thickened part3, housing 6, distance pieces 8, wall 7, and body 2 are all formed bymetal, there is a suitable electric connection between the cable 25 andthe cable 19.

The electric cable 23 is suitably insulated, and passed through a bore(not shown) in the sounding pin 1, through the cavity 5 in a flexiblemanner, so as to adapt itself to the various positions of the thickenedpart 3 of the pin y1 and the housing 6, and through a (not shown) borein the housing 6, one of the distance pieces 8 and the wall 7 of thebody 2. Thereafter it is passed alongside the body 2 and clamped theretoin a suitable (not shown) manner.

The operation of the means for determining soil resistance of subsurfacelayers as shown in FIG. 1 will now be described. As is shown in FIG. 1of the drawing, the body 2 and the pin 1 are in the normal workingposition and suspended from the flexible conduit 17 in a substantiallyvertical, substantially cylindrical hole 26 which passes through thesubsurface formation 27 .of which the soil resistance has to be measuredas a function of depth. The manner in which hole 2.6 has been formedwill be better understood after having described the way of operation ofthe present apparatus within the hole 26 as shown, and thus be describedhereinafter, in particular with reference to the apparatus as shown inFIGS. 2 and 3.

Liquid under pressure (such as pressurized water) is passed from asuitable source at the surface via the flexible conduit 17 (FIG. 1) andthe bore 15 into the cavity 11 of the body 2, and passes through thiscavity 11 along the distance pieces 8 to the entrances of the nozzles12. The liquid is ejected from the nozzles 12 in the direction of thearrows 28, thereby washing away the soil to a depth below the lower endof the body 2, but above the lower end .of the sounding pin 1. As thebottom of the hole 26 is continuously being removed by the washingaction of the hydraulic jets issuing from the nozzles 12, the body 2,which is continuously being lowered in the hole 26 by paying out theflexible conduit 17 can descend in the hole 26 unhampered, and thesounding pin 1 will penetrate in the formation under influence of theweight of the body 2.

The resistance which the soil exerts on the sounding pin 1, compressesthe pin to a certain extent. The compression of the pin by thisresistance as well as by the hydraulic pressure acting thereon, ismeasured by the straingauge 24. These measurements are communicated tothe surface via the electric cables 19 and 20 and recorded on thesurface (not shown) as a function of depth. It will be appreciated thatthe depths at which the measurements are taken are recorded by measuringthe length of the flexible conduit 17 which has been played out into thehole 26. After compensation of the inuence of the hydraulic pressure onthe recorded measurements (which pressure is linear to the length of theflexible conduit as played out below the sea level) a recording of therelationship between soil resistance and depth can be made.

Although the straingauge 24 has been shown in FIG. 1 to be located in apart of the sounding pin 1 which is located in the zone of the formation27 which is not disturbed by the hydraulic action of the jets 28 passingout of the nozzles 12, it will be understood that this straingauge 24could, with equal result, be arranged in that part of the sounding pin 1which is out of contact with the formation 27. Those types of measuringapparatuses, however, which have to be in direct contact with theformation 27, are mounted in that part of the sounding pin 1 which isinside the formation 27 during operation of the equipment.

It will be appreciated that the largest value of the Soil resistancewhich can be measured by the present device cannot be greater than theweight of the body 2 and the sounding pin 1 divided by thecross-sectional area of the sounding pin 1. For example, assuming thetotal weight of the device having a volume of 30 cubic decimetres to be240 kilograms and the cross-sectional area of the sounding pin 2 squarecentimeters, a maximum load capacity of the soil of kg./cm.2 can bemeasured in a waterfilled hole 26, if the upward forces exerted by thejets 28 are neglected. However, if liquid is used having a specificdensity greater than l, this latter figure will be somewhat smaller.When encountering formation layers having bearing capacities higher than105 kg./cm.2, the weight of the device will be insufficient to penetratethe sounding pin 1 deeper into the formation 27. However, thecharacteristics of the spring 14 have been chosen such, that under thissituation in which the full weight of the body 2 rests upon theimmovable sounding pin 1, the valve 4 is opened by the weight of thebody 2 against the action of the spring 14, thereby opening a passagebetween the cavity 11 lled with high pressure liquid and the nozzle 13.Consequently a jet of liquid will pass out of the nozzle 13 and onto theformation 27 (as indicated by 29), which jet has sufficient energy towash away the formation to a level just below the lower end of thesounding pin 1. The boundary of this washed away section has beenschematically indicated bythe dashed line 30 in FIG. l.

It will be appreciated that during this passage of the sounding pin 1through formation layers having a bearing capacity over 105 kg./cm.2, noindication of the exact value of this capacity can be obtained. Once thesounding pin has passed through such formation layer (wherein the actionof jets 29 is supported by the action of jets 28 to increase thediameter of the hole 26 sufficiently to obtain a free passageway for thebody 2) the exact values of the bearing capacity of the formation 26 canbe measured again.

It will be appreciated that the invention is not limited to theparticular design of the means for determining the soil resistance ofsubsurface layers as shown in FIG. 1 and described with referencethereto. Thus the electric equipment as described for taking themeasurements of the forces exerted on the sounding pin may widely differfrom the one as shown in the drawing. Instead of the design as shown, anamplifier may be arranged for amplifying the signals obtained from thestraingauge 24, which amplifier may be placed at a suitable location.The amplied signals are transmitted via two insulated electric cables tothe surface. These cables may be incorporated in the flexible conduit 17(like the cables 19, 20), but may also be separate therefrom or clampedthereto by suitable means.

The way in which the body 2 and the sounding pin 1 are lowered into theformation 27 will now be described in more detail. Although theequipment which can be used for this purpose and which is shown in FIGS.2 and 3 is especially designed for measuring bearing capacities offormations lying below a body of water, it will be understood that thisequipment can also be used for landwork.

The equipment as shown in FIG. 2 comprises a frame 40, which ispreferably three-legged, and equipped with two guide wheels 41, 42 whichare rotatably supported by the frame by means of a set of cardan rings.This set comprises a ring 43 pivotally supported by the frame 40 bymeans of pivots 44, 45 and a ring 46 which is pivotally supported by thering 43 by means of pivots 47, 48 (FIG. 3). The guide wheels 41, 42 arerotatably arranged around pins 49, 50 carried by the ring 46.

A guiding and protecting sleeve 51 for guiding and protecting the body 2and the pin 1 is connected to the ring 46 by means of rods 52 and 53.

FIG. 3 shows a top view of the equipment according to FIG. 2. The guidewheel 42 is positively driven by means of an electric motor 54 whichobtains its energy via a cable 55, and is connected to the wheel 42 viaa suitable (not shown) transmission.

The wheel 41 is freely rotatable around the pin 4,9 and connected via asuitable transmission (not shown) to a revolution counter 56. Thesignals obtained from this counter are, as will be explainedhereinafter, representative for the length of the flexible conduit 17which has been played out and consequently representative for the depthat which the sounding pin 1 is operating. These signals are sent via thecable 57 to a recording apparatus (not shown) where they are recorded incombination with the signals obtained from the sounding pin 1.

The ilexible conduit 17 which carries the body 2 and constitutes apassage for the liquid to be fed to the nozzles of the body 2, is passedin the form of a figure eight over the guide wheels 41 and 42. Thediameter of the wheels, and of the cable, and the friction between thewheels and the cable is chosen such that the conduit 17 is passed overthe wheels 41 and 42 at a speed dictated by the electric motor S4actuating the wheel 42, as long as the body 2 can descend. However, whenthe body 2 is not moving in a downward direction (e.g. when the jet 29is operating to break through a layer of high bearing capacity) theflexible conduit 17 will slip over the surface of the wheel 42 andconsequently the wheel 41 will no longer be driven by the conduit 17 andthe recorder which receives signals from the revolution counter 56 viathe cable 57 will indicate that the lowering of the body 2 in the hole26 has stopped.

When starting measuring operation, the frame 40 having the body 2suspended in the protecting sleeve 51, is lowered from a ship onto thebottom of the sea 58. This lowering operation is to be carried out bysuitable guide lines, cables and anchors but, since it is no part of theinvention, will not be described in detail. As the guiding andprotecting sleeve 51 enclosing the body 2 is suspended from the frame 40by means of two cardan rings 43 and 46,V the axis of the sleeve 51 willbe vertical, even if the sea bottom is not horizontal.

By starting the motor 54 which is operatively connected to the guidewheel 42, the ilexible conduit 17 is passed over the guide wheels 41 and42 and the body 2 is lowered in a vertical direction. The pin 1 onentering the bottom 58 under influence of the weight of the body 2, iscompressed and this compression (which is a function of the bearingcapacity of the soil 58) is measured and recorded in the manner asdescribed with reference to FIG. 1. At the same time, the length ofexible conduit 17 which has passed over the wheel 41 is measured by thecounter 56 and recorded together with the information obtained from thesounding pin 1.

The liquid which is being fed to the cavity 11 (FIG. l) ofthe body 1 vathe flexible conduit 17 issues from the nozzles 12 in a substantiallydownward direction and starts to erode the sea bottom 58 locally wherethe pin 1 has penetrated this bottom over some distance. The localerosive action forms the hole 26 (FIG. 1) which is of sufficientdiameter to allow the body to pass therethrough so as to follow the pin1 which is continuously being pressed into the bottom of this hole underinfluence of the weight of the body 2. The bottom of the hole iscontinuously being washed away by the action of the jets 28. The jets 29come into action only when the weight exerted on the pin 1 isinsufficient to allow further progress of the pin 1 in downwarddirection.

It will be appreciated that the present invention is not limited to thearrangement of nozzles as shown in FIG, 1. If desired, the nozzles maybe arranged according to another pattern than the one as shown in FIG.l, provided that there is always one nozzle or a set of nozzles which issuitable to erode during normal operation the soil to a level which isbelow the body 2 but above the lower end of the pin 1. Further there maybe arranged a second nozzle or set of nozzles, from which whenrelatively hard formation layers are to be passed, hydraulic jets canissue to erode the soil to a level just below the sounding pin, andvwhich nozzle(s) may be put in operation when the load exerted on the pinis insutlcient to force the pin into the soil. The valve or valvescontrolling the liquid supply to this second nozzle or set of nozzlesmay. eg., be operated electrically by receiving an electric signal fromthe recording means so as to indicate that the maximum load on the pinhas been reached. When the hard layer has been passed, the load on thepin will drop below this maximum value, and a signal will be sent to thevalve to close the passageway to the second nozzle or set of nozzles. Inanother manner the valve may be put in operation by a relativedisplacement between the pin 1 and the body 2 and put out of operationby a relative displacement between these two parts but in a directioncontrary to the direction of the rst relative displacement.

If desired, the second nozzle 13 or set of nozzles may communicate withthe interior 16 of the exible conduit 17 via a passageway which isdifferent from the cavity'11.

In another embodiment, the second nozzle 13 or set of nozzles maycommunicate with the interior of a second flexible conduit. This latterconduit and the first conduit 17 may be combined to a single body. Itwill be understood that in both embodiments as described, a biased valveoperated by the pin 1 is located in the passageway leading to the secondnozzle or set of nozzles, which valve is operated in the same manner asdescribed with reference to FIG. 1.

Reference is now made to FIGS. 4, and 6, all showing a longitudinalsection of an apparatus according to the invention, in which the bodycarrying the sounding pin is provided with two sets of nozzles. Otherthan in the apparatus according to FIG. 1, the liquid supply to thenozzles is controlled by a valve system, in such a manner that the twosets cannot operate simultaneously at full energy. The valve system isbiased by hydraulic pressure instead of by a spring as in the deviceaccording to FIG. l. As can be seen from the drawing, the FIGS. 4, 5 and6 show the valve system in different positions.

The details, in which the apparatus according to FIGS. 4, 5 and 6 doesnot differ from the apparatus according to FIG. l, have been omitted.Such details are inter alia the flexible conduit 17, the straingauge 24and the electric circuit.

In FIG. 4, the pin 61 is being forced into the formation 62 underinfluence of its own weight and the weight of the body 60. The bottompart 63 of the hole 64 is continuously being eroded by the action of thejets 65. Water under pressure is supplied to the body 60 from a suitablepump (not shown) via a flexible conduit (not shown) carrying the body60. The ow of water within the body 60 is indicated by the arrows 66.

A valve body 67 is mounted on the pin 61, which valve body is providedwith a first valve face 68, ports 69 and a second valve face 70. Thefirst or lower valve face 68 is suitable to co-operate with the lowervalve set 71 in the normal operative position of the apparatus as shownin FIG. 4, whereas the second or upper valve face 70 is suitable forcooperation with the upper valve seat 72 in the position as shown inFIG. 6, wherein the apparatus is passing through relatively hard layers.

The pin 61 and the valve body 67 are guided so as to be axiallydisplaceable with respect to the body 60, by the guides 73, therestricted part 74 of the valve housing 75 and the part 76 of this valvehousing.

The apparatus according to the invention as shown in FIGS. 4, 5 and 6comprises two sets of nozzles. The rst set consists of nozzles 77arranged in the lower wall 78 of the body 60, and the second set isformed by openings 79 arranged around the pin 61 and between the guides73. The pin 61 is urged in downward position by the difference in loadexisting between the parts of the valve body 67 exposed to the pressureprevailing in the interior of the valve housing 75 and the parts of thevalve body 67 and the pin 61, which are exposed to the pressureprevailing in the hole 64. The difference in pressure existing overthese parts is created by the resistance exerted to the flow of waterpassing through the nozzles 77 arranged in the lower wall 78 of the body60. Normally the difference in load on the various parts of the pin 61and the valve body 67 will be suicient to retain the pin in the positionas shown in FIG. 4. However, when hard layers are encountered, the pin61 will move relatively to the housing 60 and be urged into the housingunder inuence of the weight of the body 60 which is being lowered in thehole 64.

Thus, if the weight of the body 60 is, e.g. 205 kilograms, and thedifference in hydraulic load over the valve 67 and the pin 61 is 200kilograms, subsoil formations having a bearing capacity of up to 100kilograms per square centimeter can be measured when the cross-sectionof the pin 61 is 2 square centimeters. The relative position between pin61 and body 60 will then be as indicated in FIG. 4. By' meeting aresistance of a value higher than 200 kilograms, the housing 60,weighing somewhat over 200 kilograms, runs over the pin 61 (viderelative position as shown in FIG. 5) until the position as shown inFIG. 6 has been reached, in which position the passageway leading to thenozzles 77 has been closed off, and the passageway leading to the secondset of nozzles 79 which are arranged around the pin 61 and between theguides 73 is opened. The flow of liquid supplied via the exible conduit(not shown) to the body 60 then flows through the valve body 67, theports 69, the valve housing and enters the nozzles 79 at last via theannular passage between the pin 61 and the restricted portion 74 of thevalve housing 75 (see arrows 80). The dimensions of the nozzles 79 havebeen designed such that the water issues therefrom in a powerful jet 81,which is capable of eroding in the relatively hard formation layer thedirect surroundings of the pin 61 down to a level which is just belowthe lower end of the pin 61. Thus, the relatively hard layers in theformation 62 which have a bearing capacity higher than kilograms persquare centimeter may be hydraulically washed through at the locationwhere the pin 61 has to penetrate. After having passed through thesehard layers, the lower end of the pin enters softer formations. Sincethe load on the pin is then reduced, the load difference existing overthe pin 61 and the valve body 67 will push the pin partially out of thebody 60 which results in a shift of the valve system to the position asshown in FIG. 4. Consequently, the jet streams 81 are cut off and theentry to the nozzles 77 are opened, thereby forming jet streams 65 whichare able to erode the relatively hard layers of the forarntion duringthe descent of the pin 61 and the body 60 in the hole 64, since thedistance between the nozzles 77 and the hard layers has been reduced asthe pin has already protruded in the local hole 82, which has beenpre-eroded by the jets 81.

It will be appreciated that the valve system according to the FIGS. 4-6will in particular be useful for application in equipment which isapplied for measuring the bearing capacity of formations havingrelatively hard layers present therein, which are of relatively smallthickness.

An alternative of the apparatuses as shown in FIGS. 1 and 4 will now bedescribed with reference to FIGS. 7-12 which show an apparatus accordingto the invention in various positions relative to a relatively hardformation layer which is to be passed by this apparatus.

The apparatus as is schematically shown in FIG. 7 in its normal workingposition and comprises a housing 100, and a sounding pin 101 which istelescopically arranged with respect to the housing 100 and slides in atubular guide member 102 which with its lower end thereof is connectedto the lower wall of the housing 100. In this lower wall, a set ofnozzles 103 is arranged which nozzles are directed in such a manner thatthey create jet streams 104 under different angles with respect to thecentral axis of the apparatus.

A pin 105 is xed to the sounding pin 101 and slidably arranged in a slot106 of the guide 102. The sounding pin 101 is movable between twopositions which correspond with the end positions of the pin 105 in theslot 106.

Water under pressure is supplied from a suitable source (not shown) tothe interior 107 of the housing 100 via the flexible tubing 108 of whichthe lower end is clamped by clamping means 109 to the upper end of thehousing 100. The ow of water is indicated inside the housing 100 by thearrows 110 and outside the housing by the arrows 104.

The pressure drop existing in the liquid over the nozzles 103 alsoexists over the upper end and lower end of the sounding pin 101, therebyforcing the sounding pin 101 in the position as shown in FIG. 7, whereinthe pin 105 rests in the lower extremity of the slot 106 of the guidev102. It will be appreciated that as long as the forces exerted on thelower part 111 of the pin 101 which protrudes in the formation 112 aresmaller than the net hydraulic downward force acting on the soundingpin, this pin remains in the position relative to the housing 100 asshown in FIG. 7. The forces exerted on the part 111 compress thesounding pin and the compression is measured in a suitable manner, e.g.by a straingauge (not shown), similar to that described hereinabove.Since the measuring of the compression of the sounding pin and thetransport of the measuring results to the surface has already beendescribed with reference to FIG. 1, no further description thereof willbe given with reference to FIG. 7 since the same equipment may be used.

If the forces exerted on the part 111 of the sounding pin 101 exceed apredetermined'value, the sounding pin 101 will be pushed into thehousing 100. This value is in the present case equal to the net downwardforce exerted by the hydraulic pressure over the sounding pin 101increased by the relative mass of the sounding pin. This position isshown in FIG. 8, when the sounding pin 101 cornes to rest during thedownward travel thereof in the formation 112 on the top of therelatively hard formation layer 113. In the position as shown in FIG. 9,the sounding pin 101 is as far as possible retracted into the housing100 (in a position in which the pin 105 is in its extreme upper positionin the slot 106 of the guide 102) and the jets 104 which in therelatively soft formation 112 could wash away the formation to a levelbetween the lower end of the housing 100 and the lower end of thesounding pin 101 are then in a position in which they may wash away therelatively hard layer to a depth just below the lower end of thesounding pin -1. The body/pin assembly in the relative position as shownin FIG. 9 then descends through the relatively hard formation layer 113until the pin 101 passes into the underlying relatively soft formation114, into which it immediately protrudes under influence of thehydraulic force acting on the sounding pin 101. This situation isindicated in FIG. 1l. Thereafter, the jets 104 wash away the relativelysoft formation 114 to a level between the lower end of the housing 100and the lower end of the sounding pin 101 so as to form a substantiallyvertical, substantially cylindrical hole 115 through which the body 100,which is being lowered into this hole by paying out the tubular conduit108 (FIG. 7) at a substantially constant speed.

It will be understood that, if desired, the sounding pin 101 as shown inFIG. 7 may be provided with a piston having a diameter different fromthe diameter of the pin 101, on which piston acts at one side thepressure in the space 107 and at the other side the pressure whichprevails outside the housing 100.

Suitable sealing means may be provided around the sounding pin 101 aswell as around any of the other sounding pins as described in thisspecication so as to separate the high pressure hydraulic zone insidethe body 100 from the hydraulic zone outside this body.

It will further be appreciated that the body and sounding pin, asdescribed with reference to FIGS. 4-6 as well as the body and a soundingpin as described with reference to FIGS. 7-l2, may be lowered by meansof the equipment as shown in FIGS. 2 and 3. However, any other type ofequipment for lowering the body and sounding pin in the formation may beused as well for the equipment according to FIG. l as for the equipmentaccording to FIGS. 4-6 and the equipment according to FIGS. 7-12. Thus,the flexible conduit carrying the body and the sounding pin may belooped at least once around a drum (not shown), which is continuouslydriven at a substantially constant speed, and thereafter guided past ameasuring wheel, the rotation of which is measured and recorded forindicating the way length along which the sounding pin has been loweredin the formation. Obstructions met by the sounding pin in the form oflayers of relatively high bearing capacity will momentarily hamper theprogress of the body and the sounding pin in downward direction, sincethe jets will have to erode a hole through these relatively hard layers.During this stalling of the progress, the movement of the flexible tubealong the measuring wheel is stopped as the tube slips over the drivingwheel.

It will be apprecaited that the speed at which the body and sounding pindescend in the formation depends only on the speed at which the bottomof the hole is being eroded (by jets 23 in FIG. l and 65 in FIG. 4). Themaximum speed at which the body and sounding pin may descend is limitedby the rotational speed of the driving wheel (wheel 42 in FIG. 3).

I claim as my invention:

1. A method of determining the soil resistance of at least one layer ofa subterranean earth foramtion comprising the steps of:

driving a sounding pin carried by a body from the earth surface throughsaid layer utilizing the weight of said body to drive said sounding pinthrough said layer;

measuring the forces exerted on said sounding pin;

recording the forces being measured; and

washing away soil within said layer while driving said sounding pintherethrough by jetting a uid spray downwardly and substantiallyparallel to the longitudinal axis of said sounding pin in an amountsufficient to form a hole of suicient diameter to allow the body to passtherethrough.

2. The method of claim 1 wherein the step of washing away soil withinsaid layer while driving said sounding pin therethrough by jetting afluid spray downwardly and substantially parallel to the longitudinalaxis of said sounding pin comprises at least some of the time washingaway said soil to a depth above the lower end of said sounding pin.

3. The method of claim 2 wherein the step of washing away soil withinsaid layer comprises the step of washing away said soil byI jetting afluid spray downwardly and substantially parallel to the longitudinalaxis of said sounding pin to a levelat least just below the lower end ofthe sounding pin when said apparatus encounters a layer of thesubterranean earth formation which offers a resistance to said soundingpin greater than the driving force exerted on said sounding pin by theweight of said body.

4. Apparatus adapted to be lowered through a layer of a subterraneanearth formation to determine the soil resistance of that layercomprising:

a hollow elongated body; a sounding pin axially slidably connected toone end of the body; measuring elements carried by the sounding pin formeasuring forces exerted on the sounding pin; first jetting nozzle meansfor emitting a iluid jet carried by the body at the end connected to thesounding pin and opening away from the body in a direction substantiallyparallel to the longitudinal axis of the sounding pin; second jettingnozzle means for emitting a iluid jet around the sounding pin carried bythe body adjacentr the sounding pin and opening away from the body in adirection substantially parallel to the longitudinal axis of thesounding pin;

flexible conduit means connected to the end of the body opposite thefirst and second jetting nozzle means for delivering uid to the bodyfrom a source of pressurized fluid.;

passage meanslextending through the body to provide uid communicationbetween the conduit means and the rst and second jetting nozzle means;and

valve means disposed within the passage means and operatively associatedwith the sounding pin for increasing fluid ow to the second nozzle meansas the sounding pin slides inwardly with respect to the body and fordecreasing fluid flow to the second nozzle means as the sounding pinslides outwardly with respect to the body.

5. The apparatus of claim 4 wherein said passage means includes at leasta first and a second passageway in said body, said first and secondpassageways being, respectivef 1y, in communication with said first andsecond nozzle means; and wherein said valve means is arranged in saidsecond passageway, said valve means being coupled to said sounding pinwhereby said valve means is opened by a relative inward movement of thesounding pin with respect to the body, and is closed by a relativeoutward movement of the sounding pin with respect to the body.

6. The apparatus of claim 7 wherein said conduit means includes rst andsecond flexible conduit means connected to the body; wherein saidpassage means includes a rst passageway extending through the body toprovide uid communication between the rst conduit means and the rstjettng nozzle means and a second passageway extending through the bodyto provide uid communication between the second conduit means and thesecond jetting nozzle means; and wherein said valve means is arranged insaid second passageway, said valve means being coupled to said soundingpin whereby said valve means is opened 12 by a relative inward movementof the sounding pin with respect to the body, and is closed by arelative outward movement of the sounding pin with respect to the body.

References Cited RICHARD QUEISSER, Primary Examiner C. E. SNEE III,Assistant Examiner U.S. Cl. X.R. 175-50

